The present invention relates to a novel polyesterimide which is soluble in both phenol series and amide series solvent, and the preparation of the same.
Polyimide is a known polymer with outstanding heat stability and mechanical property. But it is not available for application in solution processing because it is insoluble in general organic solvents. Conventional preparation of polyimide utilizes the precursor polyamic acid for processing, followed by cyclization. However, due to difficulties in storage and the strong corrosive property of polyamic acid, handling and processing are problematic.
In order to improve the processing ability but retain the heat stability of polyimide, polyester-imides are prepared by introducing an ester group into the main chain of the polymer. However, it is necessary to use the phenol series, such as m-cresol and cresylic acid, as the solvent of conventional polyester-imide. As to the solvent of amide series, e.g., N-methyl-2-pyrrolidone (NMP), N,N'-dimethylformamide (DMF), and N,N'-dimethylacetamide (DMAC), the solubility of polyester-imide is poor. Additionally, the strong odor and the corrosive damage to skin make a phenol series solvent inappropriate for polyester-imide processing.